1. Field of the Invention
Apparatuses consistent with the present invention relate in general to a radio frequency (RF) micro-electro-mechanical system (MEMS) switch, and more particularly, to an RF MEMS switch in which electrostatic force is generated between a fixing portion and an actuator so that the actuator is prevented from sticking to a substrate.
2. Description of the Related Art
A MEMS refers to a device or system in which electric components and mechanical components are combined in a small structure. An RF MEMS refers to an RF device or system having the MEMS. The MEMS increases performance, the number of functions, and integration of the RF device, and lowers size, price, volume, and power consumption.
Generally, electronic systems operated in a high-frequency band have been developed to have a small size and weight and high performance. Accordingly, semiconductor switches, such as field effect transistor (FET) switches or pin diodes, which have been used to control signals in such systems have several drawbacks associated with bandwidth, isolation, insertion loss, power consumption, and linearity. Insertion loss refers to an RF signal transmission with a loss when a switch is turned on, and isolation refers to non-transmission of an RF signal when a switch is turned off. Linearity refers to the uniformity of a ratio of output power to input power.
The MEMS switch exhibits excellent characteristics over a very broad bandwidth. Particularly, the MEMS switch has a very broad available frequency band, a highly excellent isolation characteristic, and much less insertion loss and power consumption.
A switch is widely used as an RF device using an MEMS technique. RF switches have been applied to selective signal transmission circuits and impedance matching circuits in wireless communication terminals and systems operated in microwave or millimeter wavebands.
FIG. 1 illustrates an example of a conventional RF MEMS switching device.
Referring to FIG. 1, the RF MEMS switching device 10 comprises a semiconductor substrate 11, a pair of signal lines 13 formed on the substrate 11, and an interconnect 15 connecting between the signal lines 13.
An RF signal input through one of the signal lines 13 is delivered to the other signal line 13 through the interconnect 15. The interconnect 15 is driven by an external driving force, such as an electrostatic force, and comes in contact with the signal lines 13 or out of contact with the signal lines 13. Thus, the transmission of the RF signal through the signal lines 13 is realized by the interconnect 15.
Since the interconnect 15 is fabricated in close relation with the substrate 11 as described above, the interconnect 15 and the substrate 11 may be stuck to each other when a sacrifice layer between the interconnect 15 and the substrate 11 is removed. Further, both ends of the interconnect 15 come in contact with the signal lines 13. This obstructs the reduction of contact resistance and in turn increases insertion loss and power consumption.